Delta-sigma modulators can produce idle tones in the target frequency band (band of interest) for certain nominal DC input voltages (including input short). For example, idle tones can be caused by either modulator architecture or circuit implementation (for example, parasitic capacitance). In-band idle tones can limit SNR and dynamic range performance.
Prior techniques for suppressing/breaking idle tones include dithering to introduce randomization to break the idle tone(s), and introducing DC offset to shift the idle tone(s) to an out-of-band frequency (out of the passband).